The present invention relates to a variable speed pulley assembly. In particular, the present invention relates to a variable speed clutch or variable speed pulley assembly for use in a lawn tractor or garden tractor to vary the drive speed of the tractor while the engine speed remains constant. U.S. Pat. No. 5,897,450, the entire disclosure of which is incorporated herein by reference, discloses such a pulley assembly. Another variable speed pulley assembly is disclosed in U.S. Pat. No. 4,941,863.
The present invention is a variable speed pulley assembly for use with a drive belt having a V-shaped cross-sectional configuration for transmitting driving force to the pulley assembly and a driven belt having a V-shaped cross-sectional configuration for transmitting force driving force from the pulley assembly. The pulley assembly is supported on a support member. The pulley assembly comprises a shaft supporting the pulley assembly on the support member for rotation relative to the support member about an axis. An outer drive pulley half is fixed for rotation with the shaft on a first portion of the shaft having a first diameter. An outer driven pulley half is fixed for rotation with the shaft on a second portion of the shaft spaced apart axially from the first portion and having the first diameter.
A bushing is on a third portion of the shaft axially intermediate the outer drive pulley half and the outer driven pulley half. The bushing is movable axially in opposite directions along the third portion of the shaft between the outer drive pulley half and the outer driven pulley half. The third portion of the shaft has the first diameter. A center pulley is fixed for rotation with the bushing. The center pulley comprises an inner drive pulley half and an inner driven pulley half fixed for rotation with each other. The center pulley is rotatable with the outer drive pulley half and the outer driven pulley half about the axis.
The inner drive pulley half and the outer drive pulley half define between them a drive pulley groove. The drive belt is received in the drive pulley groove and is movable radially in the drive pulley groove between a radially innermost position and a radially outermost position. The inner driven pulley half and the outer driven pulley half define between them a driven pulley groove. The driven belt is received in the driven pulley groove and is movable radially in the driven pulley groove between a radially innermost position and a radially outermost position.